Insulated wire termination, method, and machine

ABSTRACT

A method, machine and termination for connecting two or more insulated wire ends comprises placing them in a metal tube held between fusing electrodes. The electrodes are shaped to deform the tube and wires therein with the application of fusing pressure. During fusing, pressure builds first to press the assembly together, then heat and current are applied as the tube and internal wires are compressed. Fusing current first flows from a longitudinal region of the tube equally in both direction through the tube metal to soften the tube and distribute the fusing heat broadly. As the wire insulation is burned off or flows away, current also passes through the bare wire ends to aid the fusing process. For tinned copper tubes, some of the inside tin layer flows to wet copper surfaces and dissolve copper impurities. Some tin flows to seal small spaces between the fused wires. Some of the tin on the outside surface and inside surface of the tube may vaporize. A fusing machine is also disclosed for carrying out the method that is suspended from a standard retractable winch cable so that the electrodes can be easily positioned in free space.

This is a divisional application of application Ser. No. 08/416,021,filed Mar. 31, 1995, now U.S. Pat. No. 5,660,742, issued Aug. 26, 1997.

BACKGROUND

The present invention relates generally to fused wire terminations andmore particularly to terminations in which a plurality of individuallyinsulated wires or individually insulated wires of a stranded cable arefused within a tube-like terminal or device. The present invention alsorelates to the method of making such termination and the apparatus formaking such termination.

Many attempts have been made to design methods and apparatus for quicklyand reliably terminating a plurality of individually insulated wires toa terminal or other device. One standard technique today requires theinsulation at the ends of stranded magnet wire, for example, to bemanually or chemically stripped of insulation then placed in a partialring-like device or terminal and crimped to a closed and compressedconfiguration.

A standard technique for terminating insulated transformer wire includesinserting them into a tube member that has a brazed longitudinal seamthat serves to only hold the tube shape before compression. The tube hasridges or projections on its inner surface. The assembly is cold crimpedcausing the ridges to penetrate the wire insulation to make electricalcontact with the outer surfaces of the wires therein.

These standard methods are not only time and labor consuming, butproduce irregular or mechanically weak terminations which causes hotspots when the cable carries or the wires carry electrical power.

Methods of fusing an insulated wire to a terminal or other metal deviceare also known where the insulation is driven or burned away during thefusing process. See for example, U.S. patents: Riordan U.S. Pat. No.5,111,015; Gibson, Jr. U.S. Pat. No. 3,519,778; Szantho et al U.S. Pat.No. 4,371,772.

Methods are also known for placing a number of wires in terminal orother device and fusing the assembly under heat and pressure to burnaway or vaporize the insulation and fuse the parts together. See U.S.patents A. S. Warner U.S. Pat. No. 4,034,152 and Slavin et al U.S. Pat.No. 4,538,045.

A disclosure is also known purporting to include wrapping a metal wiremesh around three individually insulated rectangular conductors andinserting the assembly into a ring terminal and welding the assembly toburn off the insulation and enhance the electrical contact of the finalproduct by the use of the wire mesh. See U.S. Pat. No 4,317,277.

Hand-held welding machines are also known that suspend from retractingwinch mounted cables for movement in free space by an operator in orderto be able to move the machine quickly from one welding location toanother and to quickly change the welding head orientation. See ARObrand Spot Welding Guns Models N297A and B, ARO Machines A Souder,Chilly-Mazarin, France.

Notwithstanding prior methods and arrangements and apparatus, the needfor faster and more reliable methods and equipment for making suchterminations continues to grow. Some of the problems with prior systemsinclude excessive manual and time consuming efforts, the inability ofmaintaining a proper fusing or welding head orientation manually justprior to fusing power application, inability to develop a reliable,reproducible, and uniform electrical connection among the fused andcompressed assembly of parts, the need to introduce an element or fillermaterial between the individual wires in order to adequately burn offinsulation, the inability to fuse magnet wire cables without producingsubstantially low production yields, and the need to use chemicals ormanual insulation stripping equipment and steps.

SUMMARY OF EXEMPLARY EMBODIMENT OF THE PRESENT INVENTION

It is an object of the present invention to provide a method, fusingmachine and final termination that solve the foregoing problems andprovide advantages and benefits beyond the capability of the prior art.

One exemplary method, according to the principles of the presentinvention, includes inserting individually insulated wire ends into ametal tube, then applying mechanical pressure with the fusing electrodesto compress the assembly transverse to its axis.

As deformation and pressure build, current is applied through theelectrodes and equally through two paths in the tube to heat the tubeand wires therein to burn off the insulation and/or cause the insulationto flow to any open spaces in the joint. Because two current paths areprovided by the tube, the system can apply greater power to the jointand the tube walls can be thinner than the case where only one currentpath is provided.

The electrode continues to apply pressure up to a predetermined limit asthe parts heat toward their plastic state to compress and fuse the nowuninsulated wires with each other and with the deformed tube to formstrong mechanical and electrical bonds among the parts.

Another aspect of the invention is to provide a method for producing agood quality and reliable electrical termination of the type described.One example of the method according to the present invention uses a tinplated or coated copper tube. Accordingly, the tin performs manyfunctions during the fusing process, such as wetting and cleaning thecopper material prior to fusing temperatures being reached, flowing tofill any open spaces to enhance joint sealing near the tube innersurface, functioning as a copper solvent to form bronze in the event anyhigh temperature zones result from the application of fusing current,and other benefits.

The wires can be of any suitable type such as magnet wire, Litz wire,insulated and uninsulated stranded cable or the like.

Production reliability is enhanced, in accordance with the presentinvention, by including the step of having the electrodes lightly butsecurely engaging the tube prior to the fusing process described above.The electrodes thus assume a "ready position" prior to initiation offusing. This enables the operator to secure the tube between theelectrodes, insert the insulated wires, check for proper positioning ofall parts prior to initiation of the fusing process. If parts are notproperly positioned, the operator can, if desired, release the electrodefrom the ready position, re-position the tube and again move theelectrodes to the ready position and reposition the wires or cable. Ifthe parts are now properly positioned, then the operator can initiatethe high pressure, high energy fusing process.

In one example according to the principles of the present invention, themachine can be stationary whereby the tube and wires or cable arebrought to the electrode fusing position.

Another arrangement affords great advantages for production, where thewire ends are generally positioned differently in space, such as aplurality of stator wires of a large motor. The present fusing machinecan be suspended from a retracting winch mounted cable to move freely inspace, thereby enabling the operator or a robot to properly position thefusing electrodes in free space. With the tube held in the readyposition, wires are inserted and the machine activated to fuse theassembly. Now, however, the operator can relatively quickly, bring themachine to the ready position, fuse a termination, sequentially, movethe machine to the next wire set in space in turn to repeat the process.

One example of the machine according to the principles of the presentinvention includes a frame and a pair of electrodes aligned for relativemovement in a direction generally perpendicular to the axis of the tubeto be held therebetween. A pair of handles mounted on the frame, one oneither side of the electrodes. A ready switch is mounted on one handle.But in order to apply fusing power, the operator must actuate twoswitches, one on each handle. Thus, both hands must be on both handles,away from the electrodes, when power is applied.

Another aspect of the invention includes a termination or terminalassembly made by one or more of the method aspects described above.

Other and further advantages and benefits provided by the presentinvention will become apparent with the following detailed descriptionwhen taken in view of the appended drawings of one exemplary embodimentof the invention, in which:

DRAWINGS

FIG. 1 is a side view of one example of a tube termination used in thepresent invention.

FIG. 2 is a front view of the tube of FIG. 1.

FIGS. 3 and 4 show the tube of FIG. 2 and a pair of fusing electrodesaccording to the present invention.

FIG. 5 is a side view of FIG. 4.

FIGS. 6 and 7 are side and rear views respectfully of the tube held bythe electrodes with the insulated wires inserted into the tube member.

FIG. 8 is a diagramatic view showing the electrode and tube/wireassembly of FIG. 7 during the application of electrode pressure butbefore the application of electrical power.

FIG. 9 is a partial exploded view of a part of the tube and insulatedwires of FIG. 8.

FIG. 10 is similar to FIG. 9 but after the application of heat andelectrical power.

FIG. 11 is an enlarged view of FIG. 10.

FIG. 12 is a perspective of a terminated tube and wire assembly madepursuant to the above described method.

FIG. 13 is similar to FIG. 12 and shows an alternate form of tubetermination.

FIG. 14 is a perspective view of one example of a machine forimplementing the method described herein.

FIG. 15 is a left side view of the machine of FIG. 14.

FIG. 16 is a perspective view of an alternate electrode shape andinsulated cable wires joined to insulated magnet wires in accordancewith a termination and process of the present invention

FIGS. 17-19 are diagramatic representations of further alternate shapeof electrodes for producing terminals with alternate cross sectionalshapes.

DESCRIPTION OF EXEMPLARY EMBODIMENTS OF PRESENT INVENTION

With reference to FIGS. 1 and 2 the present invention includes the useof a terminal tube 10 made of suitable metal such as copper or bronze orsteel depending upon the application and specific wire materials to beterminated. In a preferred embodiment, tube 10 comprises a tin-platedcylindrical tube which is easily manufactured and simply cut and tinnedin tubular form. Alternatively, tube 10 can be made from rolled sheetmetal with a soldered, welded seam, or otherwise joined seam (notshown). A preferred feature is that tube 10 should be electricallycontinuous such that current and heat will flow evenly through bothhalf-cylinders of tube 10 in a manner described below. It is alsopreferred that the tube 10 shape be cylindrical so that the operator orthe mechanical placement apparatus need not be concerned with theangular orientation of tube 10 in the electrode.

With reference to FIGS. 3-5, the method according to the presentinvention includes the use of a pair of fusing electrodes 12 and 14.Unlike low resistance welding electrodes, electrodes 12 and 14 comprisehigh resistance electrodes, typically made of tungsten or other suitablematerial, and serve to apply to the work high pressure, high heat, andsome current as further described below. Electrodes 12 and 14 aremounted for movement toward and away from each other. In the illustratedembodiment, electrode 12 is stationary and electrode 14 is mounted forvertical movement. However, if preferred, both electrodes can be mountedfor movement, and/or the electrodes can be mounted for relativehorizontal movement.

Electrode 12 has a fusing face that forms a cavity 13 for receiving tube10 generally as shown in FIGS. 3-5 and functions apply fusing pressure,heat and current throughout the bottom half of tube 10. Also, cavityfunctions to confine the flow and expansion of tube 10 and wirestherein, as described below, which enables increased pressure to beapplied to the work assembly. In the illustrated embodiment, the cavity13 is generally semicircular with approximately the same diameter as theouter diameter of tube 10 and extends to approximately half the verticaldiameter of tube 10 when the latter is placed therein.

The fusing face of electrode 14 includes a central projection 17 shapedto extend toward cavity 13. Projection 17 functions to compress the sideof tube 10 and the wires therein toward cavity 13 with a greatestpressure being applied toward the center region of the work assembly.Beveled edges 19 extend from projection 17 and cooperate to applypressure, heat, and current to the outer parts of the work assemblyduring the fusing.

After tube 10 is placed in cavity 13, the operator advances electrode 14to engage tube 10 with a slight force of about five pounds. Electrode 14thus serves to hold tube 10 in place while the insulated wires 16 areinserted into tube 10. See FIGS. 6 and 7. The operator can then inspectthe work assembly to see if all elements are properly positioned and arefree from defects. If for any reason, the work assembly elements are notin the proper position for fusing, the operator can remove wires 16,back off electrode 14 and reposition tube 10, if necessary.

Once the operator is satisfied, the operator energizes the fusingactuator switch. Accordingly, fusing head 14 is driven toward electrode12, generally as shown in FIG. 8. Pressure increases on the workassembly driving all parts together in a reduced volume of space. Fusingcurrent and heat are preferably not applied during the first 25-45milliseconds, during which tube 10 is greatly deformed and much of theair space between parts is eliminated. As seen in FIG. 8, the pressureapplied by electrode cavity 13 is applied to the bottom outer halfsurface of tube 10 and is directed toward the original axis of tube 10.The pressure applied by projection 17 is applied to the central regionof upper outer half surface of tube 10 and is directed in opposition tothe direction of the pressure applied by cavity 13. Bevel edges 19 applypressure near the outer regions of outer half upper surface of tube 10.These pressures are generally indicated by the arrows of FIG. 8.

Once a predetermined pressure or displacement is reached betweenelectrodes 12 and 14, fusing power in the form of AC current is appliedthrough electrode 14 initially through tube 10 only, through electrode12 to ground. Electrodes 12 and 14 heat to about 1900 degrees F. Becauseof the shape of tube 10 and the shapes for the electrodes, fusingcurrent flows from electrode 14 evenly through both side cylinderportions of deformed tube 10 to electrode 12. Thus current and heat isapplied evenly throughout the length for the work assembly to enhancethe integrity and reliability of the finished joint.

Accordingly, the great heat applied to the work assembly vaporizes muchof the insulation about wires 16 and causes any remaining insulation toflow away from the heat sources toward the free ends of deformed tube 10and/or toward any remaining microspaces between parts. During this time,current also begins to flow through the copper wires 16 as theinsulation burns off to expose the copper which is still under pressureand forced and deformed against other exposed copper wires and theinside of tube 10. Also, application of fusing heat and current throughtube 10 causes the inside tin coating 20 to wet some of the exposedcopper wires and to flow toward open microspaces between the deformedwires that become forced together. See FIG. 11. It should be understoodthat none of the parts amalgamate nor become liquid during the fusingprocess. The materials only soften and yield to pressure to deformagainst each other creating a mechanical bond or compression jointbetween parts. For further information about the use of tin in fusingsystems, see JOINING COPPER CONDUCTORS USING TIN-FUSING by S. Karpel,QUARTERLY JOURNAL OF THE INT. TIN RESEARCH INSTITUTE, No. 145, 1985.

FIG. 12 shows that final termination for a preferred embodimentillustrated in the previous Figures. The terminal 10 comprises anelongated bow-shaped termination for a plurality of previously insulatedwires with great mechanical integrity.

FIG. 13 shows another preferred embodiment in which the terminalincludes a terminal connector 22 extending from the tubular termination.

With reference to FIGS. 14-15, one embodiment of a machine for carryingout the method of the present invention is shown, which machine isportable and has many applications including but not limited to fusingthe ends of stator wires for large electric motors. As commonly known,large motors are difficult to move around and the common practice ofterminating stator wires therefor includes using mechanical coldcrimping apparatus. But this technique does not produce good and longterm reliable joints as described above.

The fusing machine 30 of FIGS. 14 and 15 includes a single blockU-shaped frame 32 made of aluminum or other suitable material, aircylinder 34 mounted on and main shaft 36 mounted through frame 32. Frame32 suspends in free space from eye-pins 33 and cables 35 that extend toa standard overhead mounted retractable winch (not shown). Thisarrangement enables the operator to move fusing machine 30 in free spaceto precisely position the fusing electrodes relative to the work to befused, eg the grouped ends of stator wires.

Upper electrode holder 38 is mounted to the free end of shaft 36 andcarries the upper electrode, such as that depicted as 14 in the previousFigures. Fusing machine 30 further includes a lower electrode holder 42mounted to the inside of frame 32 and carrying the lower electrode suchas that depicted as 12 in the previous Figures. Although the lowerelectrode holder 42 is stationary with frame 32 in the embodimentillustrated, it will be understood that an air cylinder and shaft can beincluded to drive holder 42 toward electrode holder 38 , if desired.

Two operator control handles 46 are mounted on the top and spaced onopposite sides of frame 32. Each handle 46 includes a control switch 48.A control panel 49 is arranged on the top center of frame 32 andincludes a selector switch 51 for enabling the operator to select one ofeight different fusing current settings depending upon the number ofwires, diameter and thickness of tube 10, the nature of the insulationon the wires, and other parameters. The program switch setting isindicated by one of the eight LEDs, lamps or digital display 53.

Frame 32 includes a number of cavities (not shown) to accommodate opticfiber cable 50, electric control cable 52 for control panel 49, airevacuation tube 54 and coolant flow 56. See U.S. Pat. No. 4,079,225 forthe use of fiber optic cable to sense the fusing temperature and thework during fusing and controlling the fusing current in responsethereto. Air tube communicates with nozzle 55 to draw off fumes from thework/electrode location during the fusing process. Electric power isapplied to machine 30 by braided cable 58 connected to the powerterminal 59.

In operation, the operator places a tube 10 in the cavity of electrode12 and presses one of the control switches 48. This causes air cylinder34 to move electrode holder 38 toward electrode holder 42 untilelectrode 14 engages tube 10 with a predetermined pressure, such as afew ounces. The operator then moves machine 30 to a position in whichthe retained tube 10 is near the wires to be terminated. The operatorinserts the wires as described above and checks for proper positioning.When satisfied, the operator must place both hands on both handles 46and throw both actuating switches 48 at the same time in order to applyfusing pressure and power to the work assembly as described above. Oncethe method described above is completed, the air cylinder willautomatically withdraw holder 38 away from the completed terminal. Theoperator can now move the machine to a new work location and repeat theprocess.

Although the electrodes shown in FIG. 14 are oriented to receive thetube and wire assembly arranged horizontally, it should be understoodthat the electrodes can be oriented to receive the work assembly in avertical orientation such as that shown in FIG. 16. With this electrodeorientation, wires can be inserted both from the top and bottom of thetube simultaneously. The wires can be of the same type or differenttypes such as the cable wires and magnet wires shown in FIG. 16.

With reference to FIGS. 16 and 17, the electrodes are shaped to formterminal 10 to include a depressed center region and a pair of wing 60portions on either side of the depressed center region. The verticaldimension of the electrodes 12 and 14 are preferably generally equal tothe length of tube 10 to impart the greatest heat to the work. However,the electrode length may be somewhat shorter than the length of tube 10with the understanding that fusing energy levels may need to beincreased to compensate for the heat sink effect created by thenon-fused portions of the tube.

It should be understood that a wide variety of electrode shapes may beused in the present invention depending upon the desired final shape ofthe termination, nature of the wires to be terminated, and other designconsiderations. For example, the electrodes of FIGS. 18 and 19 aredesigned to produce a generally rectangular cross section in the finaltermination.

It will be understood that the fusing machine, method and terminalproduct according to the present invention provide many advantages overthose of the prior art. Also, it will be understood that other andfurther modifications and changes can be made to the embodiments hereindisclosed without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. A method of joining at least two elongatedinsulated metal wires comprising:placing the insulated wireslongitudinally in an elongated metal tube having a length less than thatof the wires and having an inner surface, applying fusing pressure todeform the tube and compress the insulated wires and the tube innersurface together such that the insulated wires are pressed against otherinsulated wires or other insulated wires and the inner surface, andafter initiating and during said applying fusing pressure step, applyingto the deformed tube fusing heat and current to remove the wireinsulation from the metal wires and to soften the tube and wire metalswhile the same are under said fusing pressure, said heat and currentbeing insufficient to melt the tube or wire metals.
 2. A methodaccording to claim 1, wherein said step of applying heat and currentcomprises applying initial current at one longitudinal region of thetube and causing said initial current to flow equally in both directionsthrough the tube metal in opposite directions from said one longitudinalregion.
 3. A method according to claim 2, wherein the metal of theinsulated wires is copper based and the tube is tin-coated, the methodfurther comprising wetting at least one of said wires with tin from thetin-coating during the step of applying the fusing heat and current. 4.A method according to claim 2, wherein the metal of the insulated wiresis copper based and the tube is tin-coated, the method furthercomprising causing the tin from the tin-coating to flow during the stepof applying fusing heat and current to seal small spaces formed at leastin part by the wires within the deformed tube.
 5. A method according toclaim 2, wherein said fusing pressure is applied to a significant regionof the tube to prevent said region from deforming.
 6. A method accordingto claim 5, wherein the fusing pressure is applied to deform the tubeinto a bow shaped termination when viewed in the longitudinal directionof the deformed tube.
 7. A method according to claim 1, furthercomprising applying a slight pressure to the tube prior to and duringthe step of placing the insulated wires into the tube to hold the tubefixed in space during the step of placing the insulated wires in thetube and maintaining the slight pressure until applying greater pressuretoward the magnitude of the fusing pressure.
 8. A method according toclaim 2, wherein said step of applying the fusing heat and currentcomprises flowing current through the metal wires after the wireinsulation has been removed to further heat and soften the metal wires.9. A method of joining at least two insulated metal wirescomprising:placing the insulated wires longitudinally in an elongatedmetal tube having a longitudinal axis, applying fusing pressure todeform the tube and compress the insulated wires and the tube interiortogether, and applying to the deformed tube fusing heat and current toremove the wire insulation from the metal wire and soften the tube andwire metals while the same are under said fusing pressure, and whereinsaid tube comprises a continuous cylinder open at both ends and said atleast two wires comprise a plurality of magnet wires.
 10. A method ofjoining at least two insulated metal wires comprising:placing theinsulated wires longitudinally in an elongated metal tube having alongitudinal axis, applying fusing pressure to deform the tube andcompress the insulated wires and the tube interior together, andapplying to the deformed tube fusing heat and current to remove the wireinsulation from the metal wire and soften the tube and wire metals whilethe same are under said fusing pressure and wherein said step of placingcomprises placing the at least two insulated wires into one end of themetal tube and placing at least two wires into the other end of themetal tube.
 11. A method according to claim 10, wherein said step ofplacing comprises the first mentioned insulated wires being of differenttype from the second mentioned insulated wires.
 12. A method accordingto claim 11 wherein the step of placing comprises the first mentionedinsulated wires are magnet wires and the second mentioned wires arestranded cable wires.